TOPOLOGYCAL AND DYNAMICAL DESCRIPTION OF CARBONYLS AND PHOSPHATES IN THE INTERFACE OF LIPID MEMBRANES.

DISALVO, EDGARDO ANÍBAL; DÍAZ, SONIA BEATRIZ; FRÍAS, MARÍA DE LOS ANGELES; GORDILLO, GABRIEL; MARTINI, FLORENCIA; LAIRION, FABIANA; ALMALECK, HUGO; BEN ALTABEF, AIDA.

Salt Lake City, Utah, EEUU

Congreso; Biophysical Society 50th Annual Meeting,2006; 2006

Biophysical Society 50th Annual Meeting,2006 TOPOLOGYCAL AND DYNAMICAL DESCRIPTION OF CARBONYLS AND PHOSPHATES IN THE INTERFACE OF LIPID MEMBRANES. Disalvo, Edgardo Aníbal; Díaz, Sonia Beatriz; Frías, María de los Angeles; Gordillo, Gabriel; Martini, Florencia; Lairion, Fabiana, Almaleck, Hugo, Ben Altabef, Aida. Biophysical Society 50th Annual Meeting,  Salt Lake City, Utah, EEUU, 18-22 febrero de 2006. ABSTRACT Carbonyls and phosphates are two important sites of hydration in the lipid structure of membranes. Phosphates are esterified to different charged and non charged groups such as choline, ethanolamine and glycerol among others. This makes the interface of lipid membranes to present a heterogeneity in the hydration and polarity. The frequency of the two populations of carbonyl that appears in media of different hydrophobicities presents a maximum at the phase transition temperature. This effect disappears in the presence of carbohydrates, which shift the frequency to lower values. This suggests that the formation of hydrogen bonds between the lipid and the sugar rigidifies the interface by anchoring to the carbonyls and reducing the area per molecule. Carbonyls in the lipid interface are required for the adsorption and catalytic activity of proteases. Its exposure to the aqueous media is strongly related to the interaction of the phosphate groups to neighbor groups, such as ethanolamine or cholines.. In a DMPC interface, the absence of carbonyls reduces drastically the adsorption of proteolytic enzymes. However, in phosphatidylethanolamine, enzyme adsorbs much less than in DMPC and this interaction is not altered by the absence of carbonyls. In addition, the distribution of the two carbonyl populations is altered by arbutin but not by trehalose or other sugar. The exposure and dynamics of the carbonyl group to the water interface is strongly influenced by the group esterified to the phosphate. The head group conformation is independent of the presence of carbonyls in phosphoethanolamine monolayers but affects in phosphatidylcholines. The results suggest that the lipid interface can be described by fluctuations in the carbonyl population and the exposure of the phosphate modulated by the chemical group esterified to it.